The Spring System Description Language

The introduction of hard timing constraints to the semantics of a computation presents a set of design challenges that are signi cantly di erent from those of conventional systems, requiring the ability to guarantee that timing constraints are met. Such systems must consider the worst case, rather than the average case, behavior of the system and application software. The Spring system uses a scheduler constructing explicit plans for executing application programs to ensure that both logical and temporal constraints are satis ed. Such scheduling requires a detailed representation of the worst case run-time behavior of the application. Constructing the behavioral description requires detailed information about the properties and requirements of the application, system, and target hardware. The Spring system description language (SDL), plays vital roles in both its source and compiled forms. SDL source les enable developers to specify the properties of all parts of the system in great detail. When compiled, this information is available for use by all tools needing to use, modify, or add to it. The SDL thus provides vital support for speci cation, compilation, and execution of applications on the Spring system, as well as for specifying input information to simulations run under Spring's scheduling testbed. This document presents the many sections of the SDL in detail, discusses its roles within the Software Generation System, the use of the information it provides at runtime, and describes the set of interface routines available for use by tools wishing to use or modify SDL information stored in compiled form. This work was supported by ONR under contracts NOOO14-85-K-0398 and NOOO14-92-J-1048 and by NSF under grant DCR-8500332.